In a process for manufacturing semiconductor devices, resists such as photoresists are typically used to form an ion impurity region in a semiconductor substrate. For example, a resist film formed on a semiconductor substrate is irradiated with an active chemical ray through a mask or a reticle having a desired pattern, then developed with a developing solution, and then heated to be cured (hereinafter, referred to as “heat curing”), whereby a cured pattern of the resist film is formed. By using the formed cured pattern as an ion implantation mask or a dopant exposure mask, an element that will constitute an ion impurity region from a compound containing the element is ionized. Then, a collision of the resulting ions with the semiconductor substrate is caused (hereinafter, referred to as “ion implantation”), or the semiconductor substrate is exposed to a compound containing an element that will constitute an ion impurity region (hereinafter, referred to as “dopant exposure”). In this manner, an ion impurity region having a desired pattern is formed.
In the case where an ion impurity region is formed in a semiconductor substrate by ion implantation or dopant exposure, an ion implantation mask and a dopant exposure mask are required to be designed with high-resolution pattern processability for the purpose of forming an ion impurity region having a desired pattern. Furthermore, to form an ion impurity region having a desired pattern dimension, an ion implantation mask and a dopant exposure mask are required to be designed with rectangular pattern processability. Furthermore, an ion implantation mask and a dopant exposure mask are required to be designed with high heat resistance and cracking resistance. In particular, at the time of ion implantation, ions accelerated with high energy collide with a semiconductor substrate, so that excess heat is generated by collision energy, and hence, an ion implantation mask is required to be designed with high heat resistance and high cracking resistance so as to be capable of resisting the impact of ion implantation.
In recent years, it has been desired that, not only in ion implantation, but also in substrate processing by dry etching or ion milling, a simpler cooling system is employed to accelerate processing speed, and accordingly, a photoresist having high heat resistance has been desired.
Note that a polyimide is a resin excellent in heat resistance, and can be patterned when provided with photosensitivity. Techniques using a polyimide-based photosensitive composition as an insulating film or an ion implantation mask for semiconductor devices have been disclosed (for example, refer to Patent Literatures 1 to 3).